/Engine/Source/Runtime/Core/Public/Serialization/MemoryLayout.h
Allow the layout parameters to modify the given DDC key string. Since layout parameters are part of e.g. material shadermap ID, they should result in two different DDC entries for two different IDs, even if binary layouts happen to be compatible.
void AppendKeyString ( [FString](API\Runtime\Core\Containers\FString) & KeyString ) const